1. Field of the Invention
The present invention relates to a device for treating milling products, comprising a housing, a rotor rotably mounted inside the housing and the rotor including at least one pocket for reception of steam-containing milling products, which is to be treated, an inlet in the housing for steam-containing milling products to be passed on to the pocket and an outlet in the housing for milling products to a steam proof discharge device, the pocket being a provided with a radially outwards facing opening, and a steam outlet in the housing. The present invention does also relate to a method for treating milling products according to which steam-containing milling products is fed via a housing to a pocket in a rotor rotating in the housing, the milling products is, under influence of the centrifugal force, moved radially outwards towards the circumferential surface of the housing and then thrown out through an outlet for milling products when the pocket has been brought in communication therewith.
2. Description of the Related Art
When lignocellulose containing products are milled, for example defibration of woodchips to pulp, where large amounts of energy are supplied to the milling apparatus or the defibrator, large amounts of steam are generated. The energy content of the steam is considerable and must be taken care of in order to improve the economy of the plants for pulp production. Generally, the steam is separated from the pulp after the defibration in so called cyclones which operate with centrifugal separation. However, in these devices clogging problems often arise due to the fact that the moist pulp deposits on the walls and tubes of the cyclone forming lumps which grow and eventually the separation comes to an end, so that the production has to be stopped and the separator must be cleaned.
It is usual, in order further to process the pulp, after the defibrator to include a milling machine, refiner, by which the pulp is finely ground before being supplied to the steam separator cyclone.
These problems are, according to the Swedish patent SE 510 247 C2, solved with a device for treating milling products. That device comprises a housing in which there is rotatably arranged a rotor having a number of pockets which in turns are in communication with an inlet for milling products. The milling products are thrown out by a centrifugal force through a radially outwards facing opening in the pockets and further to a milling products outlet in the housing when the pocket and the milling product outlet are in communication with each other. The steam is then blown out from the pocket into a steam outlet in the housing when they are in communication. The inlet and the steam outlet are arranged parallel to the rotor shaft. The inlet, the milling products outlet and the steam outlet are angularly displaced in relation to each other.
The purpose of the present invention is to provide a device which cleans the steam from milling products particles to a higher extent then what take place in the prior art.
That object is attained with a device for treating milling products according to the introductory paragraph which is characterized in that the rotor pocket is provided with a radially inwards facing opening for steam which can be put in communication with the outlet for steam, at least once for every revolution during the rotation of the rotor. A method according to the introductory paragraph is characterized by the fact that the remaining steam is thereupon emptied radially inwards when the pocket is brought into communication with the steam outlet of the housing.
An advantage of this device is that it cleans the steam effectively since remaining particles would have to move against the action of the centrifugal force in order to leave with the outgoing steam, which consequently does not occur.
According to one embodiment the outlet for steam includes a projection provided with at least one channel or a space and at least one radially outwards facing opening, said projection extending a distance in the central area of the rotor so that the opening of the projection can be brought into communication with at least one of the radially inwards facing openings of the rotor pockets.
This brings the advantage that the radially inwards facing openings of the rotor pockets are sealed by the projection, except when they coincide with the opening of the projection.
The inlet for steam-containing milling products, the outlet for milling products and the outlet for steam are angularly displaced in relation to each other.
The inlet for steam-containing milling products is preferably oriented substantially axially in relation to the rotor in a flange of the housing but can of course be arranged in another way, for example tangentially.
The rotor pocket can have a through passage, in which case the rotor pocket is sealed off at the housing flanges or the rotor exhibit a wall on the one side of the rotor pocket, in which case the rotor pocket is sealed against a flange of the housing. In addition thereto, the outer circumference of the rotor is preferably sealed relatively the housing.
The rotor can be provided with an arbitrary number of rotor pockets, but suitably with at least five rotor pockets and preferably eight rotor pockets.